CINCINNATI (Reuters) - Six in 10 Americans believe the use of corn to make ethanol has raised food prices and caused more people to go hungry, the latest evidence of a growing global backlash against alternative "green" fuels.

The Hormel Hunger Survey released on Monday also showed 53 percent of Americans polled believe government subsidies for ethanol production will help reduce U.S. dependence on foreign oil, but nearly as many -- 47 percent -- oppose the subsidies because they increase food prices.

Last week Jean Ziegler, the United Nations Special Rapporteur on the right to food, called for a five-year moratorium on biofuels, saying it was a "crime against humanity" to convert food crops to fuel at a time when there are more than 850 million hungry people in the world.

The findings were based on an Internet survey of 807 Americans conducted September 25-30 in conjunction with America's Second Harvest, a food bank network. Hormel Foods, a Minnesota-based meat processor, sees the direct effects of corn price rises, since corn is the main U.S. livestock feed.

U.S. corn prices are up about 50 percent in the last two years despite record harvests due to booming ethanol demand.

"We all want the United States to be energy-independent, or at least closer to it," Hormel Foods Chairman and Chief Executive Jeffrey Ettinger told the Ohio Hunger Summit in Cincinnati.

"But is increasing ethanol production really a good thing if in the process we also increase the financial burden on American families?"

Support for ethanol production has become a staple in politics in recent years, particularly during campaign swings through corn-dependent Iowa, which kicks off the voting season in the presidential process in January.

The powerful U.S. farm lobby, along with giant biofuels processors like Archer Daniels Midland, have been champions of ethanol and "biodiesel" made from vegetable oils.

Aggressive support including tax credits and import tariffs has driven a boom in biofuels production in the United States and Europe but also helped drive prices for corn, rapeseed, soybeans and soybean oil higher.

Democratic presidential hopeful Sen. Barack Obama and Iowa Democratic Sen. Tom Harkin unveiled a stand-alone bill in October to require 18 billion gallons of renewable fuels to be blended with U.S. gasoline supply by 2016.

An energy bill the Senate passed in June would mandate a four-fold increase in ethanol use in motor gasoline, to 36 billion gallons by 2022.

U.S. ethanol plants are forecast to produce about 6.5 billion gallons in 2007, according to the Renewable Fuels Association.

The hunger survey found 64 percent of Americans believe U.S. hunger has worsened in the last year, with 13 percent saying they or someone in their family had gone to bed hungry in the past month.

Sixty percent said they have had to cut back on the quality or quantity of food they buy because of higher prices, while 29 percent said they expected to ask for food from a food bank or other charitable organization in the future.